Realtime HDR algorithms

OData support
Rajacsics Tamás
Department of Automation and Applied Informatics

When creating a virtual image it is necessary to reproduce real world experience as closely and convincingly as possible. The century-old problem of displaying the natural light conditions on a device with limited dynamic range originates from photography.

With modern graphics hardware high dynamic range (HDR) texture formats can be used to store actual luminance values, making it possible to map colours to the displayable range in real time.

The procedure of scaling real life dynamic ranges to the displayable domain is called tone mapping. While scaling it is necessary to maintain the original colours and luminance ratios. In the last decade several methods were invented to make the mapping possible. This paper shows the details of these methods with regard to their real time implementations.

If the virtual world is animated, just like in the case of video games, it is also possible to recreate temporal effects of the human eye or the camera. Using tone mapping, simulating the adaptation of our eye is only one step away. With a simplified model of the human eye’s behaviour realistic adaptation can be achieved.

Further real world effects can be generated using HDR luminance values. One of the most commonly known phenomena is the so called bloom effect. It appears when a strong beam of light scatters inside the eye or the lens of a camera creating a bright halo around the light source.

When implementing the discussed methods both the visual quality of the result image and the performance of the program is very important due to its real time application. Satisfying both requirements necessitates optimization and balancing between the two aspects, making the task a challenging problem for engineers.


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